Which procedures are used to confirm the diagnosis of pigmented purpuric dermatoses?

A skin biopsy helps to confirm the diagnosis of a pigmented purpuric eruption and aids in excluding cutaneous T-cell lymphoma, which in its early stages may closely mimic a pigmented purpuric dermatitis both clinically and histologically.
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Pigmented purpuric dermatitis affecting the trunk. Some of the lesions show the characteristic orange-brown, speckled, cayenne pepper–like discoloration that is the hallmark clinical sign of a capillaritis. Men are more frequently affected than women. If the lesions are pruritic, then the term itching purpura is sometimes used. Early cutaneous T-cell lymphoma, purpuric clothing contact dermatitis, and drug hypersensitivity reactions should be considered in the differential diagnosis.

Lichen aureus is the name given to localized pigmented purpuric dermatitis or capillaritis. In this patient, the skin on the extensor surface of the elbow is affected.

Histologic features of a skin biopsy sample obtained from a patient with lichen aureus shows extravasation of erythrocytes and a perivascular T-cell infiltrate.

Endothelial cell swelling is a histologic feature of capillaritis. This biopsy sample was obtained from a patient with lichen aureus.

Hemosiderin deposition is seen in dermal macrophages in this biopsy sample obtained from a patient with lichen aureus.

Capillaritis affecting the lower legs is known as Schamberg disease. In Schamberg disease, irregular plaques and patches of orange-brown pigmentation develop on the lower limbs.

The authors and editors of Medscape Reference gratefully acknowledge the contributions of previous authors, John D Wilkinson, MD, MBBS, MRCS, FRCP, and Cedric C Banfield, BSc, MSc, MBBS, MRCP(UK), to the development and writing of this article.